Power hammer



Marchi-7, 1959 E. w. RlsTow 2,877,820

' POWER HAMMER Filed Dec. 17, 1956 nited States Pate PWER HAMMER Edward W. Ristow, Wauwatosa, Wis., assignor to Milwaukee Electric Tool Corporation, Milwaukee, Wis., a corporation of Wisconsin Application December 17, 1956, Serial No. 628,708

Claims. (Cl. 153-21) The present invention relates in general to improvements in the construction and operation of power hammers of the type having an impact member adapted to be rapidly reciprocated from a rotary source of power so as to impart successive blows against work to which the implement is applied. l

The primary object of the invention is to provide an improved power hammer assemblage which is simple and compact in construction and highly eiective in use.

Some of the more specific objects of the invention are as follows:

To provide an improved portable motor driven hammer unit in which a reciprocable impact member is most effectively and rapidly actuated by a rotary power driven element.

To provide an improved universally movable power hammer having a shoe directly applicable and movable along the work and an impact member cooperable with the shoe and adapted to be rapidly alternately retracted from the work by a revolving power driven element and projected against the work by resilient means.

To provide an improved power hammer assemblage in which the striking member is operated from a power source such as an electric motor through gearing and a one-way friction drive which effectively protects the gear teeth against local wear and injury due to the repeated impact blows delivered by the hammer.

To provide a durable hammering device especially adapted to close seams along sheet metal duct assemblages or the like by delivering rapid successive blows against the work through an impact member adapted to be repeatedly retracted by a gear driven rotary element having the gear teeth most effectively protected by a simple drive adapted to uniformly distribute the wear thereon.

To provide a simple and sturdy peening hammer of the manually manipulable portable type which may be manufactured and sold for diverse uses at moderate cost, and which is safely operable at maximum etlciency.

These and other still more specific objects and advantages of the invention will be apparent from the following description.

A clear conception of the features constituting the present improvement and of the construction and operation of a commercial electric motor driven portable power hammer embodying the invention, may be had by referring to the drawing accompanying and forming a 2,877,820 Patented Mar. 17, 1959 engaging shoe and a fragment of the impact member housing, but showing this member in striking position relative to the work engaging shoe;

Fig. 3 is an enlarged central section through the work engaging shoe and the impact member confining casing of the same hammer, showing the impact member retracted as in Fig. 1, but the section having been taken perpendicular to the plane of the section in Fig. 1, along the line 3 3;

Fig. 4 is a likewise enlarged central section through the hammer unit similar to that of Fig. 3, but showing the impact member in striking position as in Fig. 2;

Fig. 5 is a similarly enlarged bottom or end view of the work engaging shoe and impact member of the same power hammer;

Fig. 6 is an exploded likewise enlarged central section through the impact member rotary retracting mechanism of the improved unit; and

Fig. 7 is a diagram showing a typical so-called Pittsburg lock for a sheet metal duct seam.

While the invention has been shown and described herein as having been embodied in an electric motor driven portable hammer especially adapted to peen progressive ilanges along sheet metal work or the like, it i-s not the intention to restrict the improvement to such assemblages; and it is also contemplatedthat specific descriptive terms employed herein be given the broadest interpretation consistent with the actual disclosure.

Referring to the drawing, the improved portable power hammer shown therein by way of illustration, comprises in general, a casing 8 having a work engaging shoe 9 secured to one end and a lateral opening 10 near its opposite end interconnected by a bore 11 in the shoe 9 and adjoining bores 12, 13 in the casing 8 forming an intervening passage; an elongated hammer member 14 having an impact head 15 slidably confined within the shoe bore 11 while its opposite end shank 16 is likewise confined within the smaller casing bore 12 and i-s provided with a lateral lug 17 directed toward the casing opening 10; a helical compression spring 18 housed within the larger casing bore 13 and coasting with the casing 8 and with the member head 15 to constantly urge the member 14 toward the work engaging end surface 19 of the shoe 9; a rotor 20 journalled in the casing 8 and having a pair of eccentric pins 21 journalled therein and projecting into the smaller casing bore 12 for lsuccessive engagement with the member lug 17; a rotary element or main gear 22 rotatably supported upon a central cylindrical portion 23 of the rotor 20 and being drivingly connectable with the latter by a one-way helical spring friction clutch 24; a motor housing 25 secured to the casing 8 at the opening 10 and enclosing an electric motor the power output shaft 26 of which is provided with a pinion 27 meshing with the gear 22; and a control switch for the propelling motor operable by a trigger 28 associated with the manipulating handle 29 ofthe unit.

The elongated casing 8 and shoe 9 are preferably formed of wear resistant metal, and the shoe 9 is detachably secured to the casing 8 adjacent to the larger bore 13 by means of screws 31 or the like in order to facilitate assembly and dismantling of the hammer mechanism. The casing 8 may be likewise detachably secured to the motor housing 25 for like purposes, and the impact member 14 is also formed of wear resisting metal and is provided with an elongated groove 32 which is slidably cooperable with a pin 33 mounted in the casing 8 in order to guide the member 14 and to prevent rotation thereof about its central axis, see Figs. 1 to 4. The work im pinging end of the impact head 15 is cam shaped for progressively turning down a sheet metal flange 30 along a duct to form a so-called Pittsburg lock or seam, see

Fig. 7. The tool is guided along the work and held in proper position relative to the impact head by surfaces 19", and the leading portion of the shoe is provided with a recess 19' which permits entrance of the upstanding flange 30 as the tool advances while the cam surface on the head 15 forms and closes the seam, the tool being supported with its surface 19 resting on the seam. The laterally projecting lug 17 is formed integral with the impact member 14 and the shank 16 of this member is cut away adjacent to the lug 17 in order to permit free revolution of the member retracting pins 21, as shown in Pigs. 1 to 4 inclusive.

The helical compression spring 18 which is normally concealed within the medial bore 13 of the casing 8, co-

acts with the enlarged head 15 of the member 14 through a retainer ring 35 at one end, and reacts at its opposite end against the casing 8 through another retainer ring 36, see Figs. l to 4. Upon removal of the screws 31, the shoe 9, member 14, spring 18, and rings 35, 36 may be removed from the casing 8 by merely jockeying the pins 21 out of the path 0f reciprocation of the impact member 14. The pins 21 may be rotatably mounted in antifriction bearings 37 confined within the rotor 20 as shown in Fig. 1, and this rotor may be likewise mounted in similar bearings 38 within the opening 10. The reduced end 39 of the rotor 20 beyond its medial portion 23 is also preferably journalled in an anti-friction bearing 40, and the motor shaft 26 may be likewise journalled in such a bearing 41. The hub of the gear 22 is rotatably supported upon the medial oil grooved rotor portion 23, and is frictionally embraced by one end portion of the clutch spring 24 the opposite end of which likewise embraces the adjacent end of the rotor 20. A pair of snap rings 42 and the gear end surface 22 properly position the spring 24 in the assemblage.

The motor housing may be formed of several sections detachably united by screws 43 in a well known manner, and some of which may be constructed of relatively light but durable metal, and the pistol grip handle 29 may have the electric motor energizing conductors 44 i" extending therethrough and cooperating with a control switch enclosed within this handle and which is operable by the trigger 28. This housing 25 may also be provided with a motor cooling vent 45 as illustrated in Fig. 1, and the entire assemblage is manipulable with the aid of the handle 29 and may be moved universally in any desired direction. In order to aid in maintaining the shoe 9 in contact with the work, this shoe 9 and the casing 8 are preferably of relatively heavy and massive construction as compared to the housing 25.

When the improved power hammer unit has been properly constructed and assembled as hereinabove described, its normal use in producing elongated anges along the edges of sheet metal work or the like, is as follows. The propelling motor may be operated at will by manipulating the trigger 28 thereby causing the pinion 27 to rotate the gear 22 at high speed and simultaneously revolving the rotor 20 and the pins 21 through the helical spring clutch 24. As each of the two pins 21 engages the lug 17 of the impact member 14, as in Fig. 3, it lifts the hammer head 1S away from the work contacting surfaces and compresses the spring 18, and when the lug engaging pin 21 passes beyond the lug 17 the compressed spring 18 immediately expands 'and becomes effective to deliver striking movement to the member 14 and its head 15. This impact action takes place twice during each revolution of the rotor 20 and the hammer blows are therefore repeated in rapid succession.

While the improved power driven implement is being thus operated, the shoe 9 may be firmly applied to and advanced along the work, and when the work to be performed involves the progressive formation of a seam along the edge of a sheet metal duct, the sheet metal flange may be conned within the inclined recess 19 of the shoe 9 while the adjacent shoe surface 19 is maintained in contact with the adjoining seam portion of the work. The continued progress of the hammer along the sheet metal structure will Ythen cause the reciprocating impact head 15 to deliver rapid successive and progressive blows against the upstanding sheet metal flange 30 while the cam surface of the head 15 will cause this flange to fold over against the adjacent sheet 46 shown in Fig. 7, thus producing a neatly peened flange along the work to any desired extent. During this flange forming operation the handle 29 may be utilized to advance the unit without obstruction due to the inclined disposition of the guiding recess 19 in the shoe 9, and the Weight of this shoe and of the casing 8 will absorb annoying vibration resulting from the hammer blows.

Whenever one of the hammer retracting pins 21 comes into engagement with the impact member lug 17, the helical clutch spring 24 which frictionally embraces both thc hub of the gear 22 and the adjacent periphery of the rotor 2i), will be wound into rm engagement with these elements thus subjecting the teeth of the gear 22 adjacent to the active pin 21 to local high pressure. But as soon as the lug engaging pin 21 is carried free of the lug 17 andthe compression spring 18 becomes effective to deliver n hammer blow the clutch spring 24 will release its grip slightly, thus allowing other gear teeth to be presented adjacent to this pin 21. This action causes all gear teeth to be progressively subjected to equal pressure and wear and thus enables the impact spring 18 to function with maximum effect in delivering the blows, while also relieving the intermeshing teeth of the gear 22 and pinion 27 of local excessive shock and wear due to the impacts and also eliminating excess back-lash, thus not only producing smoother operation but also prolonging the life of the mechanism. This improved clutch 24 therefore constitutes an important feature of the present improvement.

From the foregoing detailed description of a typical commercial embodiment of the invention, it will be apparent that the improved structure in fact provides a power hammer which is simple and durable in construction, ilexible in adaptation, and highly effective in use. The device can be utilized to produce elongated seams with utmost rapidity and precision, and the driving gears are effectively protected against shock and excessive wear by the improved clutch spring 24 which is interposed between the main gear 22 and the hammer retracting rotor 20. The anti-friction bearings 37', 3S. and 41 eliminate excessive friction losses and may be kept well lubricated at all times since they are constantly enclosed and protected, and the entire unit may be readily assembled or dismantled by merely manipulating a few screws. The improved portable unit has proven highly satisfactory and successful in actual use, and may obviously be utilized for diverse purposes.

It should be understood that it is not desired to limit the present invention to the exact details of construction and operation of the motor driven power hammer herein specifically shown and described, for various modifications within the scope of the appended claims may occur to persons skilled in the art.

I claim:

l. In a power hammer, a casing having a bored work engaging shoe at one end and a coaxial bore provided with a lateral opening near its opposite end, an elongated member having spaced cylindrical portions slidable within said coaxial bores and being provided at one end with an impact head cooperable with the work engaging said shoe while its opposite end portion is provided with a lateral lug directed toward said opening, a spring coacting with said member between said bores to constantly urge said head toward said shoe, several pins projecting into said casing through said opening and being revolvable to successively engage said lug to compress said spring and to release the lug to permit the spring to impart impact movement to said member head, a rotor supporting said pins, a motor driven gear for rapidly revolving said rotor, and a helical clutch spring frictionally embracing said rotor and the hub of said gear.

2. In a power hammer, a casing having a bored work engaging shoe at one end and a coaxial bore provided with a lateral opening near its opposite end, an elongated member having cylindrical portions guided for reciprocation within said bores and being provided at one end with an impact head cooperable with the work engaging said shoe while its opposite end portion is provided with a lateral lug directed toward said opening, a spring enacting with said casing and said member to constantly urge said head toward said shoe, several pins projecting into said casing through said opening and being revolvable to successively engage said lug to compress said spring and to release the lug to permit the spring to impart impact movement to said member head, a rotor revolvably supporting said pins within said casing opening, a power driven gear having a hub journally coaxially of said rotor, and a helical clutch spring fric tionally embracing said gear hub and said rotor to positively drive the latter in one direction only.

3. In a power hammer, a casing having a bored work engaging shoe at one end and a coaxial bore provided with a lateral opening near its opposite end, an elongated member having spaced cylindrical portions slidable within said coaxial bores and being provided at one end with an impact head cooperable with the work engaging said shoe while its opposite end portion is provided with a lateral lug directed toward said opening, a spring coacting with said member between said bores to constantly urge said head toward said shoe, a rotor having thereon at least one lateral projection extending into said casing through said opening and which is revolvable to alternately engage said lug to compress said spring and to release the lug to permit the spring to impart impact movement to said member head, a power-driven gear for rapidly revolving said rotor, and a helical clutch spring frictionally engaging said gear and said rotor to drive the latter.

4. In a power hammer, a casing having a bored work engaging shoe at one end and a coaxial bore provided with a lateral opening near its opposite end, an elongated member having cylindrical portions guided for reciprocation within said bores and being provided at one end with an impact head cooperable with the work engaging said shoe while its opposite end portion is provided with a lateral lng directed toward said opening, a spring coacting with said casing and said member to constantly urge said head toward said shoe, a rotor revolvably supporting at least one lateral projection extending into said casing through said opening and which is revolvable to alternately engage said lug to compress said spring and to release the lug to permit the spring to impart impact movement to said member head, a power-driven gear having a hub disposed coaxially of said rotor, and a helical clutch spring frictionally embracing said gear hub and said rotor to positively drive the latter in one direction.

5. In a power hammer, a casing having a bored work engaging shoe at one end and a coaxial bore provided with a lateral opening near its opposite end, an elongated member having spaced cylindrical portions slidable within said coaxial bores and being provided at one end with an impact head cooperable with the work engaging said shoe while its opposite end portion is provided with a lateral lug directed toward said opening, a helical spring coacting with said casing and said head to constantly urge the head toward said shoe, a rotor having thereon at least one eccentric projection extending laterally through said casing opening and which is revolvable to alternately engage said lug to compress said spring and to release the lug to permit the compressed spring to impart impact movement to said member head, a power-driven gear for rapidly revolving said rotor, and a helical clutch spring frictionally engaging coaxial portions of said gear and said rotor to positively drive the latter in one direction.

References Cited in the file of this patent UNITED STATES PATENTS 1,106,306 Hoal Aug. 4, 1914 1,747,842 Phillips Feb. 18, 1930 1,796,255 Waite Mar. 10, 1931 1,954,620 Connell Apr. 10, 1934 2,071,281 George Feb. 16, 1937 2,201,023 Brown May 14, 1940 2,233,937 Hexdall Mar. 4, 1941 2,397,700 Sloan Apr. 2, 1946 2,646,100 Gibson July 2l, 1953 FOREIGN PATENTS 167,286 Great Britain Aug. 4, 1921 

